The invention includes scrub testing devices and related methods. Embodiments of the invention are directed to devices and methods related to high throughput scrub testing and the like. Other embodiments of the invention are directed to devices and methods of performing testing and analyzing variables related to scrub testing including evaluation of scrubbing media, e.g., cleaning formulations, abrasive media, and the like; the testing of resistance of coatings to scrubbing with given formulations or media; the testing of scrubber devices or brush materials; stain resistance of materials; and testing the durability of coatings, for example.
Scrub resistance is the ability of paint or a like film or coating of material to resist abrasive cleaning that might remove the paint or film from the surface. Scrub resistance testing is a critically accepted test in the evaluation of the performance of such coating formulations. Scrub testing analysis can also be applied to materials that are not, strictly speaking, coatings, or applied as a film.
The details of standard scrub testing are set out in various testing methods. In North America, for example, scrub testing is defined by two different ASTM methods: D2486 “Scrub Resistance of Interior Latex Flat Wall Paints” and D4213 “Wet Abrasion Resistance of Interior Paints.” ASTM D2486 is the most standard protocol used in North America. For ASTM D2486, it is well known that a large number of parameters affect the results of the testing, which create a large variation in test results. Many versions of this test are labor intensive and require constant attention from a human operator.
The device used in the ASTM method can be a standard abrasion tester unit, e.g., a BYK-Gardner™ ‘Scrub’ Abrasion Tester Model AG-8100, to evaluate the resistance of a material to wear, most commonly a material on a substrate. The material, for example, can be in the form of a solid material, a coating, a composite or a combination of the three. In the standard test, the tester operates by moving a fixture including a brush, sponge or the like, under a constant load, in a linear, reciprocating motion, over the material. Liquids, powders or slurries can be added to the fixture to alter its ability to wear the material. Evaluation of the fixture effectiveness, or alternately the resistance of material to wear, in the presence or absence of additives, is usually monitored as a function of time or number of strokes. Conversely, the unit is also used to assess the ability of the additive to remove the material from the substrate. Therefore, the unit and test is frequently used to evaluate the effectiveness of formulations to clean a substrate. Furthermore, the Gardner™ tester is commonly used in a variety of other tests, such as stain cleaning, stain resistance, scum cleaning, wear testing, adhesion testing, washability, film streaking, and wear resistance.
In a brief example of a standard test, and with reference to ASTM D2486, a coating is applied to a black plastic panel (wet film thickness 0.007 in) and allowed to dry for a set period of time, usually 7 days. The coated panel is then mounted on a linear motion machine like that referred to above, that moves a single nylon brush back and forth over the panel. To accelerate failure, a shim is added under the center of the scrub area, and abrasive scrub media is applied. The machine is stopped when a human operator observes a continuous black line, and the number of cycles observed for the sample being tested to failure is recorded.
As noted above, the test requires a human operator in performing all or many of the steps of the test and monitoring the test. Furthermore, the test is done on one sample at a time, in series, due to the nature of the test unit and the requirement that an operator monitor the test.
Due to the above noted deficiencies of standard scrub testing devices and methods, especially in view of the labor intensive procedure required, there is a demand to develop a high throughput test that would allow for fast and accurate screening of a large number of samples which preferably correlates well to the current method. The invention satisfies the demand. Other limitations of the prior art device and method are also satisfied by the invention as will be detailed herein as well as new investigative applications for such a device.